This invention relates to the field of mattresses and innersprings, particularly to a modular mattress and modular innerspring, which is made up of a plurality of modules held together in side by side relationship by a retainer which extends around the periphery of the modular mattress and modular innerspring. The individual modules may be of whatever size and number needed to make a twin, twin extra long, full, full extra long, queen and king size mattress or innerspring.